I have some "reviews" code from a company that should display the review on a page within Joomla. the code is:

<!--Your plug-in code can be customised to looklike your website using the following styling elements..SCMyWebsitePlugin-score.SCMyWebsitePlugin-score div.SCMyWebsitePlugin-mlsLinkli#SCMyWebsitePlugin-firstItemli#SCMyWebsitePlugin-lastItem#SCMyWebsitePlugin-main#SCMyWebsitePlugin-reviewListDiv-->

Custom module edit screen ... options ... prepare content ... should allow plugins to be processed by the module. Alternatively edit the Tineymce plugin not to strip code so that you don't need an extension to insert the code. Or use JCE editor https://extensions.joomla.org/extension/jce/ it has more options.